TRYPANOSOMIASIS EXPEDITION TO THE CONGO 45 
occasions a slight rise of temperature and loss of vivacity has accompanied one of the 
irregularly appearing intervals during which parasites have been seen in the peripheral 
blood. This monkey has been infected for nearly three months. 
We have again failed, even with large closes of blood containing huge numbers 
of trypanosomes, to infect two dog-face monkeys (Cynocephalus). 
Transmission Experiments 
We have attempted to repeat the transmission experiments made by Bruce, in 
Uganda, with the tse-tse fly. These flies are rather numerous in the bush along the 
river banks on either side of Leopoldville, and a fair number are daily brought to 
the laboratory by a gang of boys supplied for the purpose by the local authorities. 
Practically all the flies brought in by them have been Glossina palpalis (native name, 
' mavekwa '). Unfortunately, we have had the greatest difficulty in obtaining monkeys 
and have only been able to use two for these experiments. Both in the Congo and in 
the Gambia, experiments have shown that the guinea-pig is, perhaps, the laboratory 
animal most susceptible to Trypanosoma gambiense. We, therefore, determined to 
employ it, lacking monkeys, in our transmission experiments. At the time of writing 
both experiments with monkeys remain unsuccessful, and only one, a direct trans- 
mission experiment with guinea-pigs, in which the flies were made to feed alternately 
on an infected and an uninfected animal, has given a positive result. 
In conclusion, we wish to thank Dr. Inge Heiberg, who has been attached to 
the expedition by the Government of the Congo Free State, for his untiring kindness 
and the help he has given us in our work. 
